Mitochondrial branched-chain alpha-ketoacid dehydrogenase kinase. Catabolism and synthesis of leucine, isoleucine and valine are finely balanced, allowing the body to make the most of dietary input but removing excesses to prevent toxic build-up of their corresponding keto-acids. This is the butyryl-CoA dehydrogenase, subunit A domain 3, a largely alpha-helical bundle of the enzyme BCDHK. This enzyme is the regulator of the dehydrogenase complex that breaks branched-chain amino-acids down, by phosphorylating and thereby inactivating it when synthesis is required. The domain is associated with family HATPase_c pfam02518 which is towards the C-terminal.